致密气藏压裂用支撑剂导流能力评价及优化

Evaluation and Optimization of Conductivity of Fracturing Proppants for Tight Gas Reservoirs

为降低致密气储层改造成本,探究了石英砂取代压裂用陶粒支撑剂的可行性。采用裂缝导流仪对石英砂和陶粒支撑剂的长期导流能力进行评价,并结合数值模拟开展导流能力与采收率相关性的研究,从而优化支撑剂类型。结果表明:在闭合压力作用下,石英砂和陶粒支撑剂的导流能力随着时间呈现初期递减快、随后递减变缓的趋势,20~40目石英砂与陶粒的导流能力呈现半对数关系递减,40~70目、70~140目的石英砂和陶粒支撑剂的导流能力呈现两段式线性关系递减;导流能力下降的主要原因是支撑剂的破碎,在裂缝闭合8 h以内破碎率增加幅度较快,随后趋于平缓,这与导流能力的变化规律一致;随着支撑裂缝导流能力提高,采收率和稳产期累积产气量逐渐增大,当导流能力大于5μm^(2)·cm时增幅逐渐减缓;可以用石英砂支撑剂代替陶粒支撑剂,渗透率为(0.01~0.10)×10^(-3)μm^(2)的气藏,选用20~40目石英砂支撑剂,渗透率为1.00×10^(-3)μm^(2)的气藏,选用40~70目石英砂支撑剂。

The feasibility of quartz sand replacing ceramsite proppant for fracturing was studied in order to reduce the reconstruction cost of tight gas reservoir.The long-term seepage capacity of quartz sand and ceramsite proppant was evaluated by using fracture seepage capacity meter,and the correlation between the seepage capacity and recovery efficiency is studied by numerical simulation,so as to optimize the type of proppant.The results show that under the closing pressure,the seepage capacity of quartz sand and ceramsite proppant decreases rapidly with the increase of time at the initial stage,and then decreases slowly.The seepage capacity of 20~40 mesh quartz sand and ceramsite decreases in a semi-logarithmic relationship;The seepage capacity of 40~70 mesh and 70~140 mesh quartz sand and ceramsite proppant shows a two-stage linear decreasing relationship.The main reason for the decrease of the seepage capacity is the breaking of proppant.The proppant breaking rate increases rapidly within 8 hours of fracture closure,and then tends to be gentle,which is consistent with the varying law of the seepage capacity.With the improvement of the seepage capacity of supported fracture,the recovery efficiency and the cumulative gas production in the stable production period gradually increase.When the seepage capacity is greater than 5μm^(2)·cm,their increase gradually slows down.Quartz sand proppant can be used instead of ceramsite proppant.The 20~40 mesh quartz sand proppant should be used for the gas reservoirs with the permeability of(0.01~0.10)×10^(-3)μm^(2);the 40~70 mesh quartz sand proppant should be used for the gas reservoirs with the permeability of 1.00×10^(-3)μm^(2).